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1

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The structure of Mo4Cl8(PEt3)4: How unrecognized disorder previously reduced the quality of the refinement (1991)

Cotton, F. Albert ; Shang, Maoyu

Springer

Journal of cluster science 2 (1991), S. 121-129

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ISSN: 1572-8862

Keywords: Molybdenum tetranuclear cluster ; rectangular ; triethylphosphine ligand ; preparation ; crystal structure

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Abstract The preparation and structure of the title compound were reported several years ago by McCarly and co-workers ((1978).J. Am. Chem. Soc. 100, 7900). Curiously, it was reported that refinement of the structure converged at exceptionally high figures of merit (R=0.126;R w =0.158), but no reason was given. In view of a recent observation in this laboratory (Chen and Cotton (1991).J. Am. Chem. Soc. 113, 5857) that a similar type of compound, [Re4Cl8(μ-O)2(μ-OMe)2]2− exhibited a subtle but elegant disorder, we reexamined the crystal structure of the title compound. It is found to have 92% of the Mo4 rectangles in one orientation (the only one previously included in the refinement) and 8% in an orientation perpendicular to the main one. In both orientations the ligand positions are approximately the same. The figures of merit are nowR=0.041;R w =0.064. The three structure parameters previously reported are now only slightly different: Mo-Mo=2.210(1) vs. 2.211(3) Å; Mo-Mo'=2.897(1) vs. 2.901(2) Å; angle Mo-Clb-Mo=74.2[8]° vs. 74.4(2)°. We report here the complete structure.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00702953

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2

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The synthesis and structural analysis of Pt2Ru4(CO)18 and the products obtained from its reactions with 1, 2-bis(diphenylphosphino)ethane (1993)

Adams, Richard D. ; Chen, Gong ; Wu, Wengan

Springer

Journal of cluster science 4 (1993), S. 119-132

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ISSN: 1572-8862

Keywords: Platinum ; ruthenium ; crystal structure ; heteronuclear cluster

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Abstract From the reaction of Ru(CO)5 and Pt(COD)2, COD = 1, 5-cyclooctadiene, the new platinum-ruthenium heteronuclear cluster complex Pt2Ru4(CO)18,1, was obtained in 60% yield.1 has a folded ladder-like structure with alternating pairs of ruthenium atoms and platinum atoms. The cluster of1 can be split to yield the known compound PtRu2(CO)8(η2-dppe),2, (54% yield) by reaction with 1, 2-bis(diphenylphosphino)ethane, dppe, at 25°C. When1 was treated with excess dppe at 40°C, thebis-diphos compound3, PtRu2(CO)6(μ-η2-dppe)2 was obtained (39% yield). Under the similar reaction conditions,2 was converted to3 in 44% yield. All these complexes were characterized by single crystal X-ray diffraction analyses. Compounds2 and3 both contain a triangular cluster of one platinum and two ruthenium atoms, but in2 the bidentate ligand, dppe, chelates the platinum atom and in3 the two dppe ligands bridge the two Pt-Ru metal-metal bonds. Crystal data for1: space group C2/c,a=12.542(2)Å,b=15.350(4)Å,c=15.252(3)Å, β=105.32(2)°,Z=4, 2192 reflections,R=0.025. For2: space group P21/c,a=14.351(2)Å,b=13.486(3)Å,c=19.218(3)Å, β=108.48(1)°,Z=4, 3029 reflections,R=0.027. For3: space group P21/c,a=18.836(6)Å,b=15.559(5)Å,c=23.259(7)Å, β=111.26(2)°,Z=4, 4204 reflections,R=0.038.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00702713

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3

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Preparation and structural characterization of the hexatungsten cluster complex (EDTEH)2[W6(μ3-Cl)8Cl6], (EDTEH=(MeO2CCH2)2N(H)CH2CH2N(CH2CO2Me)2+ (1993)

Adams, Richard D. ; Chen, Gong ; Huang, Jianquan

Springer

Journal of cluster science 4 (1993), S. 271-277

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ISSN: 1572-8862

Keywords: Tungsten ; chloride ; hexatungsten ; crystal structure

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Abstract The hexanuclear tungsten cluster complex [W6(μ3-Cl)8Cl6]2−,1 was isolated as a salt of the cation (MeO2CCH2)2N(H)CH2CH2N(CH2CO2Me)2+, EDTEH+, by crystallization from methanol solvent of the product obtained from the reaction of (H3O)2[W6(μ3-Cl)8Cl3] with the disodium salt of ethylenediaminetetraacetic acid. The compound was charcterized by single-crystal X-ray diffraction analysis. The cluster anion contains an octahedral arrangement of six tungsten atoms with chloride ligands bridging the eight triangular faces of the cluster and one chloride ligand terminally coordinated to each of the six tungsten atoms. The cation (EDTEH)+ achieves its positive charge by protonation of one of the nitrogen atoms. Crystal data: space group = P21/a,a=10.689(2) Å,b=22.931(6) Å,c=12.093(3) Å, β=98.41(2)°,Z=2, 2476 reflections,R=0.028.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00703743

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4

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Preparation and structural characterization of a hexanuclear molybdenum (II) cluster containing carboxylate ligands (Bu4N)2[Mo6(μ3-Cl)8(O2CMe)6] (1993)

Adams, Richard D. ; Chen, Gong ; Huang, Jianquan

Springer

Journal of cluster science 4 (1993), S. 151-157

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ISSN: 1572-8862

Keywords: Molybdenum ; acetate, carboxylate ; hexamolybdenum ; crystal structure

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Abstract The hexamolybdenum cluster complex [Mo6(μ3-Cl)8(O2CMe)6]2−, 1 was isolated as the Bu4N+ salt in 71% yield from the reaction of (Bu4N)2[Mo6(μ3-Cl)8Cl6] with AgO2CMe in CH2Cl2 solvent. The compound was characterized by single crystal X-ray diffraction analysis. The cluster contains an octahedral arrangement of six molybdenum atoms with eight chloride ligands bridging the eight trianglar faces and six carboxylate ligands terminally coordinated through one oxygen atom to each of the six molybdenum atoms. Crystal data: space group =P21/n,a=10.713(3)Å,b=14.43(1)Å,c=21.919(4)Å, β=94.37(2)°,Z=2, 1965 reflections,R=0.036.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00702715

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5

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Synthesis, characterization and x-ray structure of V3(μ3-O)(μ-Cl)Cl6(μ-η1-η1-PhNHNH2)2(PhNHNH2)2(THF) · 6THF: A new binding mode for phenylhydrazine (1993)

Murray, H. H. ; Novick, S. G. ; Armstrong, W. H. ; [et al.]

Springer

Journal of cluster science 4 (1993), S. 439-451

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ISSN: 1572-8862

Keywords: Vanadium ; phenylhydrazine ; nitrogenase ; crystal structure

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Abstract Addition of phenylhydrazine to a mixture of VCl3 · THF/N,N-propyl-bis (salicyladimine) and sodium hydride yielded a trinuclear vanadium complex, V3(μ3-O)(μ-Cl)Cl6(μ-η1-η1PhNHNH2)2(PhNHN H2)2(THF), containing two bridging and two terminal phenylhydrazine ligands. The product has been crystallographically characterized (P21/n, a=12.949(2) Å,b=24.061(4) Å,c=22.504(4) Å, β=107.22(1) deg.,V=6697(2) Å3 withZ=4) and was found to contain the first example of bridging monosubstituted hydrazine (phenylhydrazine) ligands.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00703736

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6

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Effects of higher-order structure of poly(3-hydroxybutyrate) on its biodegradation. II. Effects of crystal structure on microbial degradation (1993)

Nishida, Haruo ; Tokiwa, Yutaka

Springer

Journal of polymers and the environment 1 (1993), S. 65-80

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ISSN: 1572-8900

Keywords: Biodegradable plastic ; microbial degradation ; bacterial poly(d-(−)-3-hydroxybutyrate) ; crystal structure ; physiological behavior

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract As one of a series of studies concerning the relationship between the higher-order structure and the biodegradability of a biodegradable plastic, the effects of the crystal structure of the plastic on microbial degradation were investigated. Bacterial poly(d-(−)-3-hydroxybutyrate) (PHB) films which had a wide range of crystallinity were prepared by the melt-quenching method. Results of the microbial degradation indicated that the development of crystallinity evidently depressed the microbial degradability. From scanning electron microscopy (SEM) observations, it is suggested that the microbial degradation proceeded in at least two manners. One was preferential degradation of the amorphous region leaving the crystalline lamellae intact, which was considered to be a homogeneous enzymatic degradation over the surface. The other was nonpreferential spherical degradation on the surface. The SEMs indicate that the spherical holes were the result of colonization by degrading bacteria. The holes varied in size and number with the change of crystal structure. Therefore, it is considered that the crystal structure of PHB also influenced the physiological behavior of the degrading bacteria on the PHB surface.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01457654

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7

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The characterization of high-tech materials: Perspectives, challenges, trends (1991)

Ortner, Hugo M. ; Wilhartitz, Peter

Springer

Microchimica acta 104 (1991), S. 177-214

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ISSN: 1436-5073

Keywords: atomic structure ; crystal structure ; microstructure ; constructions ; topochemistry ; graphite ; glassy carbon ; pyrolytic carbon ; microelectronics ; carriers of information ; refractory metal alloys ; life time ; recrystallization ; fatigue ; photon probe techniques ; electron probe techniques ; ion probe techniques ; electrical field probes

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract From the Stone Age on, developmental periods of mankind carry the names of materials. Materials determine the applicability of key technologies and these are in turn of major significance for the economic success and the social development in modern society. Today's high-tech materials are the consequence of an improved understanding of the structure and composition of matter and of the interplay of microstructure and minor and trace constituents. We can distinguish four basic dimensional structural categories of materials: (a) the atomic structure level; (b) the crystal, glassy or amorphous structural level; (c) the microstructural level; (d) the level of constructions. As an example, these structural levels are described in some detail for graphite, a material used extensively throughout Analytical Chemistry. Decisive differences at the microstructural level result in graphitic materials with very varying properties: polycrystalline electrographite, glassy carbon, and pyrolytic graphite. Examples for the use of these materials in ETAAS are discussed. Structural features together with topochemical and trace chemical characteristics are studied today by a wide variety of analytical instrumentation and methods of modern materials analysis which can be grouped into four categories of techniques: (a) photon probe techniques; (b) electron probe techniques; (c) ion probe techniques; (d) electrical field probes. The most important of those techniques are discussed shortly with respect to their main characteristics as lateral and depth resolution, detection sensitivity, additional bonding or structural information, depth profiling possibilities etc. The constructions are the ultimate level of a materials structure. Structures of microelectronic components reach dimensionally into the domain of microstructure whereas constructions in heavy industry are of meter-ton dimensions. Progress in the use of materials as carriers of information is visualized by a morphological comparison of the sound tracks of conventional records with the information imprinted in optical discs. It is important to conceive materials as dynamic systems with limited lifetime. Fatigue and recrystallization are prominent relevant phenomena which must be studied by microstructural and topochemical methods. Dispersion strengthened microalloys like TZM, HT-molybdenum and NS-tungsten are discussed as examples how materials can be improved with respect to their extended use under extreme conditions. Again, a thorough structural and topochemical characterization was the basis of a successful respective materials development although a multitude of relevant topochemical questions still remain to be solved. Lifetime investigations are an essential tool of materials development as well as quality control. Relevant investigations for various tube materials for ETAAS are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01245508

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8

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Clinical pharmacokinetics and tolerability of alpidem in healthy subjects given increasing single doses (1991)

Jonkman, J. H. G. ; Bianchetti, G. ; Grasmeijer, G. ; [et al.]

Springer

European journal of clinical pharmacology 41 (1991), S. 369-374

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ISSN: 1432-1041

Keywords: Alpidem ; Anxiolytics ; pharmacokinetics ; tolerance ; metabolites ; sedation ; adverse events

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Medicine

Notes: Summary In a double-blind, placebo-controlled, crossover experiment in 21 healthy male volunteers, aged 19 to 27 y, the pharmacokinetics and tolerance of the new anxiolytic drug alpidem (SL80.0342) and its three major metabolites were studied after single doses of 25, 50, 100 and 200 mg. Plasma concentrations of alpidem (in 20 subjects) and metabolites (in 6 subjects) were measured by HPLC over a period of 54 h after dosing. Cmax, tmax and AUC(0–54) and, when possible, t1/2 were determined for alpidem and metabolites and the dose linearity of the parameters was investigated. The time to peak of alpidem was dose independent in most subjects and was short (1–4 h); the mean values at the four dosing levels were 1.9, 1.7, 1.6 and 1.8 h. The peak concentration increased with the dose, the mean values being 17, 34, 88 and 115 ng · ml−1, respectively. In 50% of the subjects cmax tended to stabilize between the 100 and 200 mg dose. Dose linearity was also present for the AUC, which plateaued between the 100 and 200 mg dose in only 3 out of 20 subjects; the mean AUC was 119, 281, 669 and 1117 ng · ml−1 · h, respectively. The apparent half-life of elimination appeared to be dose independent, mean values at the increasing dosing levels being 18.7, 19.9, 18,1 and 17.9 h. A similar relationship between the kinetics parameters and dose of the alpidem was observed for the metabolites SL83.0912, SL80.0522 and SL83.0725. The formation of metabolites was not saturated as their AUCs relative to corresponding alpidem AUCs were not dose related. Thus the kinetics of alpidem and its three major metabolites were linear after doses of 25 to 200 mg. The drug was well tolerated by most of the subjects. Sedation and dizziness occurred mainly after the 100 and 200 mg doses.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00314970

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9

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Pharmacokinetics of caffeine in patients with decompensated type I and type II diabetes mellitus (1991)

Zysset, T. ; Wietholtz, H.

Springer

European journal of clinical pharmacology 41 (1991), S. 449-452

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ISSN: 1432-1041

Keywords: Diabetes mellitus ; Caffeine ; pharmacokinetics ; P-450 mono-oxygenase

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Medicine

Notes: Summary Diabetes may alter the pharmacokinetics of aminopyrine and antipyrine, which are used to assess liver function. Caffeine has recently been used to test liver function, but the effect of diabetes on caffeine kinetics is not known. The kinetics of caffeine has been examined in patients with decompensated Type I and Type II diabetes and in two age- and sex-matched control groups. In both types of diabetes the apparent caffeine clearance, half-life, and apparent volume of distribution were similar to controls. It is concluded that decompensated diabetes does not influence the cytochrome P-448 mono-oxygenase system responsible for caffeine metabolism.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00626367

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10

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Pharmacokinetics and haemodynamic effects of a single oral dose of the novel ACE inhibitor spirapril in patients with chronic liver disease (1993)

Krähenbühl, S. ; Grass, P. ; Surve, A. ; [et al.]

Springer

European journal of clinical pharmacology 45 (1993), S. 247-253

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ISSN: 1432-1041

Keywords: Liver cirrhosis ; Spirapril ; ACE inhibitor ; pharmacokinetics ; haemodynamic effects ; liver function tests

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Medicine

Notes: Summary The pharmacokinetics and haemodynamic effects of orally administered spirapril, a novel angiotensinconverting enzyme (ACE) inhibitor, have been investigated in patients with liver cirrhosis (n=10), in patients with chronic, non-cirrhotic liver disease (n=8) and in a control group of healthy subjects (n=16). The absorption and elimination of spirapril did not differ between patients with liver disease and control subjects. In contrast, the bioavailability of spiraprilat, the metabolite responsible for the pharmacological action of spirapril, was significantly reduced in patients (AUC 820 μg·h·l−1, 923 μg·h·l−1 and 1300 μg·h·l−1 in patients with cirrhosis, patients with non-cirrhotic liver disease and in healthy subjects, respectively. Compared to healthy subjects, cirrhotic patients had a reduced rate constant of spiraprilat formation (1.10 h−1 in patients vs. 2.00 h−1 in control subjects) while the elimination half-life of spiraprilat was not different. The effect of spirapril on diastolic blood pressure was decreased in patients with chronic liver disease as compared to the controls. Thus, the pharmacokinetics of spirapril was unchanged in patients with different types of liver disease, including cirrhosis. However, the bioavailability of spiraprilat and hypotensive effect of spirapril were reduced in patients.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00315391

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